1. Field of the Invention
The present invention relates to a thermally conductive sheet used, e.g., in the heat radiation/cooling structure of a heat-generating electronic component and a method for manufacturing the thermally conductive sheet.
2. Description of the Related Art
The following thermally conductive sheets or thermally conductive materials have been proposed as a conventional thermally conductive sheet used in part of the heat radiation/cooling structure of heat-generating electronic components or the like mounted on a substrate. Depending on the package structure of equipment, when the influence of a volatile organic gas generated from the thermally conductive sheet on the function of electronic components can be ignored, a thermally conductive sheet that includes a silicone polymer and a thermally conductive filler generally is used. Typical examples of this thermally conductive sheet are disclosed in JP 2(1990)-166755 A, JP 2(1990)-196453 A, and JP 6(1994)-155517 A. However, the thermally conductive sheets of these publications include low molecular-weight siloxane, which is volatilized by heat generated from the heat-generating electronic components. Therefore, when the package of equipment should be sealed hermetically, those thermally conductive sheets are not suitable. In many cases, a thermally conductive epoxy adhesive or the like is used as a thermally conductive material for heat-generating electronic components in the sealed electronic equipment.
The amount of heat generated from heat-generating electronic components increases with higher performance and smaller size of the components. Particularly, it becomes very difficult to cool the components in sealed electronic equipment. Moreover, the thermally conductive epoxy adhesive or the like is used in paste form and has a high viscosity, causing many problems in assembly such as poor workability and a long time required for curing. Also, conventional materials are not resistant sufficiently to heat generated from the heat-generating electronic components.